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Timothy
G. Prather
University of Tennessee Extension
With
the extreme heat and drought this year, the risk of silo fires
may be increased. Crops harvested too dry will not produce
quality silage and will increase the risks of silo fires.
Fire risks are even greater if your silo has air leaks through
cracks and around doors.
Make
sure your silo is in good repair. Inspect it carefully and
seal any cracks to keep air out. Check the condition of doors
and make sure they are sound and fit tightly.
Ensile
crops at 50 - 68 percent moisture content. Check the moisture
content with a moisture meter or use an oven-drying method
to determine crop moisture content. You cannot accurately
judge moisture content by sight or by touch. Too much moisture
results in seepage and silo damage; too little moisture can
result in a fire. Correct moisture is required for good feed.
Using
a distributor will increase the amount of silage you can store
by 10 percent by making full use of the silo. The distributor
will also result in even distribution and even packing without
a hard core; thus, fewer air pockets and better silage. Even
distribution also protects the structure and foundation from
failure.
Haylage
can dry several percentage points in a short period of time
on hot, sunny, breezy days. For example, alfalfa cut at 85
percent moisture can often be baled at 18 percent in two days.
With this in mind, time your field operations to allow the
chopper to keep pace with the mower/conditioner. Any breakdowns
or delays can allow the forage to dry too much for ensiling.
Either add water when filling the silo or bail the crop later
for hay.
Make
sure the fire department does not compound your problems if
a silo fire does occur. The fire department should not pump
thousands of gallons of water into the silo. The water will
not soak through the silage, and may channel down along the
walls instead of reaching the fire. Wetting agents are not
much help, and they contaminate the silage, rendering unburned
silage unfit for feed. Silos are not designed as water tanks,
and soaking the silage may cause structural damage or collapse.
Oxygen-limiting
silos, such as Harvestore: silos, can explode if a fire is
not handled properly. Two firemen were killed in Georgia on
August 5, 1993 when they applied water and foam to a fire
in an oxygen-limiting silo. The explosion blew the roof off,
sending one fireman to the ground over 100 yards away and
the other through the roof of the nearby metal building. Two
firemen on the ground were injured by debris. The top 15 feet
of the silo were severely damaged by the explosion and an
adjacent silo dented by the debris.
The
only safe methods for controlling fires in oxygen-limiting
silos are to close all hatches (but allow pressure to vent
from the top hatch) and inject large volumes of carbon dioxide
through the bottom of the silo.
Fires
in conventional silos can be controlled during early stages
by probing to locate the hot spots and injecting water directly
into the fire. This practice is more effective than dousing
from the top, and it uses much less water. Advanced fires
are often best left to burn themselves out. If the fire has
burned enough silage that the unloader cannot function, the
remaining silage is probably useless as feed. Even if the
fire is put out, the silo may be too dangerous to unload by
hand. Fires in concrete silos do little harm to the structure,
so prevent spread of fire and allow it to bum out.
For
more information on silo fires, obtain a copy of publication
PB 1307, Silo Fires - Prevention and Control, from your county
Extension office. And remember - safety is no accident. It
is a responsibility and a way of life.
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Disclaimer
and Reproduction Information: Information in NASD does not
represent NIOSH policy. Information included in NASD appears
by permission of the author and/or copyright holder. More
NASD Review: 04/2002
This
news release was distributed by the University of Tennessee
Agricultural Extension Service, University of Tennessee Agricultural
Extension Service, Knoxville, Tennessee 37901. Publication
date: August 1993.
Timothy
G. Prather, Agricultural Safety Specialist, Agricultural Engineering
Department, University of Tennessee Agricultural Extension
Service, Knoxville, Tennessee 37901.
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